Log-log charts

  • Thread starter Thread starter Walt Welton-Lair
  • Start date Start date
W

Walt Welton-Lair

Hi,

I'm using Excel 2002 and am trying to create a simple log-log plot. Making
the y-axis logarithmic is easy - it's a check-box option under Scale tab of
the Format Axis dialog. But for the X axis the dialog does not have that
option. My XY data is valid (all positive values). There's web sites that
say you can do this (e.g.
http://cstl-cst.semo.edu/venezian/Utilities/graphs.htm). Why doesn't my
Excel support it???

Any help is appreciated.

Walt
 
Hi Walt,

Sounds like your chart maybe a line chart (x-axis is category) instead
of true xy scatter.
Right click the chart and choose chart type...
Make sure its a xy-scatter and then you should be able to specify Log
scale the same way you have for the y-axis.

Cheers
Andy
 
Never mind...

I just discovered that you can do it if you set the chart type to scatter
plot. Linear plots don't support it. You can then change the data series
formatting so that it looks like a linear plot.

So why exactly does Excel not support logarithmic X axes in its linear chart
type? It's very misleading the way it's set up.
 
Thanks - that's what I just discovered.

Andy Pope said:
Hi Walt,

Sounds like your chart maybe a line chart (x-axis is category) instead
of true xy scatter.
Right click the chart and choose chart type...
Make sure its a xy-scatter and then you should be able to specify Log
scale the same way you have for the y-axis.

Cheers
Andy
Click to expand...
 
Walt -

You need to make an XY Scatter chart. In an XY Scatter chart, the X
values are treated as numerical variables, and therefore they have logs.
In a Line chart, the X values are treated as non numerical categories.
Aside from their treatment of the X variable, Scatter and Line charts
are nearly identical: series can be formatted the same way in either
type of chart, and the other chart elements also behave the same.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______
 
Walt -

To manny who make charts, a scatter chart is a chart with markers only,
while a line chart has points connected by lines. In Excel, the
distinction is made between scatter charts with numerical category
values (X data), and line charts with categorical X values. These
categorical labels have no numerical values (other than perhaps the
ordinal numbers 1, 2, 3,...), but instead are merely labels for the
axis, no matter what value appears to be in the label.

It's plenty confusing at first, though it makes sense after you think
about it. Too bad they didn't come up with better terminology.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______
 
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